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  <div class="question_difficulty">
   难度：Easy
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  <div>
   <h1 class="question_title">
    70. Climbing Stairs
   </h1>
   <p>
    You are climbing a stair case. It takes
    <em>
     n
    </em>
    steps to reach to the top.
   </p>
   <p>
    Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
   </p>
   <p>
    <strong>
     Note:
    </strong>
    Given
    <em>
     n
    </em>
    will be a positive integer.
   </p>
   <p>
    <strong>
     Example 1:
    </strong>
   </p>
   <pre>
<strong>Input:</strong> 2
<strong>Output:</strong> 2
<strong>Explanation:</strong> There are two ways to climb to the top.
1. 1 step + 1 step
2. 2 steps
</pre>
   <p>
    <strong>
     Example 2:
    </strong>
   </p>
   <pre>
<strong>Input:</strong> 3
<strong>Output:</strong> 3
<strong>Explanation:</strong> There are three ways to climb to the top.
1. 1 step + 1 step + 1 step
2. 1 step + 2 steps
3. 2 steps + 1 step
</pre>
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   <h1 class="question_title">
    70. 爬楼梯
   </h1>
   <p>
    假设你正在爬楼梯。需要
    <em>
     n
    </em>
    &nbsp;阶你才能到达楼顶。
   </p>
   <p>
    每次你可以爬 1 或 2 个台阶。你有多少种不同的方法可以爬到楼顶呢？
   </p>
   <p>
    <strong>
     注意：
    </strong>
    给定
    <em>
     n
    </em>
    是一个正整数。
   </p>
   <p>
    <strong>
     示例 1：
    </strong>
   </p>
   <pre><strong>输入：</strong> 2
<strong>输出：</strong> 2
<strong>解释：</strong> 有两种方法可以爬到楼顶。
1.  1 阶 + 1 阶
2.  2 阶</pre>
   <p>
    <strong>
     示例 2：
    </strong>
   </p>
   <pre><strong>输入：</strong> 3
<strong>输出：</strong> 3
<strong>解释：</strong> 有三种方法可以爬到楼顶。
1.  1 阶 + 1 阶 + 1 阶
2.  1 阶 + 2 阶
3.  2 阶 + 1 阶
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